Many chemical separation analyses, such as gas and liquid chromatography, require the chemical sample to be temperature-controlled throughout the analysis. A chromatograph comprises an inlet where the sample is introduced, an oven containing an analytic column where the separation takes place, and a detector where the constituents of the sample are detected and recorded. Each of these parts of the instrument is temperature-controlled to ensure the integrity and repeatability of the analysis. An analysis performed at a constant controlled temperature is referred to as isothermal. To perform an isothermal analysis, the analytic column is typically placed in a temperature-controlled chamber, often referred to as an oven, which is preheated to the desired temperature. A non-isothermal analysis, in which the column temperature is gradually raised over time, is also common, especially for samples with relatively massive components that would otherwise take a long time to elute from the column.
Conventional chromatographic ovens typically use convection technology to heat and maintain the interior of the chamber, and hence the analytic column, at the desired temperature. However, conventional ovens are relatively large in comparison to an analytic column which they are intended to heat and, as a result, are very power inefficient. In addition to cost, a side effect of power inefficiency is that the oven is slow to heat and cool, resulting in reduced sample throughput and productivity.
Another goal when performing a chromatographic analysis is to quickly heat the analytic column to the desired temperature. The use of radiant sources to heat the analytic column is becoming more widespread. A factor to consider when using a radiant source to heat the analytic column is the directionality of the radiant energy provided by the radiant source. For example, light waves are directional so that the line-of-sight between the source and the analytic column is a consideration. Another factor to consider when implementing a radiant source is the phenomenon of thermal gradients, which may result in uneven heating of the analytic column.
Therefore, it would be desirable to maximize heat transfer between a radiant energy source and an analytic column. Further, it is desirable to minimize thermal gradients in an analytic column.